Charged particle beam system and method of operating the same

ABSTRACT

A charged particle beam system comprises a particle beam source having a particle emitter at a first voltage, a first electrode downstream of the particle beam source at a second voltage, a multi-aperture plate downstream of the first electrode, a second electrode downstream of the multi-aperture plate at a third voltage, a third electrode downstream of the second electrode at a fourth voltage, a deflector downstream of the third electrode, an objective lens downstream of the deflector, a fourth electrode downstream of the deflector at a fifth voltage; and an object mount at a sixth voltage. Voltage differences between the first, second, third, fourth and fifth voltages have same and opposite signs.

FIELD

The present disclosure relates to charged particle beam systems andmethods of operating charged particle beam systems in which a pluralityof particle beamlets are directed onto an object surface.

BACKGROUND

A conventional charged particle beam system in which a plurality ofparticle beamlets is directed onto an object is known from WO2005/024881. The system is an electron microscope in which a pluralityof primary electron beamlets are focused in parallel to form an array ofprimary electron beam spots on the object. Secondary electrons generatedby the primary electrons and emanating from respective primary electronbeam spots are received by a charged particle imaging optics to form acorresponding array of secondary electron beamlets which are supplied toan electron detection system having an array of detection elements suchthat each secondary electron beamlet is incident on a separate detectionelement. Detection signals generated from the detection elements areindicative of properties of the object at those locations where theprimary electron beam spots are formed.

By scanning the array of primary electron beam spots across the objectsurface, it is possible to obtain an electron microscopic image of theobject. It is desirable to obtain images at a high resolution and a highthroughput. For this purpose it is desirable to achieve small primaryelectron beam spots on the object and to be able to scan the primaryelectron beam spots rapidly across the object surface.

Additional prior art is disclosed in U.S. Pat. No. 7,960,697 B2.

SUMMARY

The present invention has been accomplished taking the above problemsinto consideration.

Embodiments of the invention provide a method of operating a chargedparticle system, wherein the method comprises: extracting a particlebeam from a source; performing a first accelerating of the particles ofthe beam; forming a plurality of particle beamlets from the beam afterthe performing of the first accelerating; performing a secondaccelerating of the particles of the beamlets; performing a firstdecelerating of the particles of the beamlets after the performing ofthe second accelerating; deflecting the beamlets in a direction orientedtransverse to a direction of propagation of the particles of thebeamlets after the performing of the first decelerating; performing asecond decelerating of the particles of the beamlets after thedeflecting of the beamlets; and allowing the particles of the beamletsto be incident on an object surface after the performing of the seconddecelerating.

Other embodiments of the invention provide a method of operating acharged particle system, wherein the method comprises: extracting aparticle beam from a source; performing a first accelerating of theparticles of the beam; forming a plurality of particle beamlets from thebeam after the performing of the first accelerating; performing a firstdecelerating of the particles of the beamlets; performing a secondaccelerating of the particles of the beamlets after the performing ofthe first decelerating; deflecting the beamlets in a direction orientedtransverse to a direction of propagation of the particles of thebeamlets after the performing of the first decelerating; performing asecond decelerating of the particles of the beamlets after thedeflecting of the beamlets; and allowing the particles of the beamletsto be incident on an object surface after the performing of the seconddecelerating.

Further embodiments of the invention provide a method of operating acharged particle system, wherein the method comprises: extracting aparticle beam from a source; performing a first accelerating of theparticles of the beam; performing a second accelerating of the particlesof the beam after performing the first accelerating; performing a firstdecelerating of the particles of the beam after the performing of thesecond accelerating; forming a plurality of particle beamlets from thebeam after the performing of the first decelerating; deflecting thebeamlets in a direction oriented transverse to a direction ofpropagation of the particles of the beamlets; performing a seconddecelerating of the particles of the beamlets after the deflecting ofthe beamlets; and allowing the particles of the beamlets to be incidenton an object surface after the performing of the second decelerating.

Still further embodiments of the invention provide a method of operatinga charged particle system, wherein the method comprises: extracting aparticle beam from a source; performing a first accelerating of theparticles of the beam; performing a first decelerating of the particlesof the beam after performing the first accelerating; performing a secondaccelerating of the particles of the beam after the performing of thefirst decelerating; forming a plurality of particle beamlets from thebeam after the performing of the second accelerating; deflecting thebeamlets in a direction oriented transverse to a direction ofpropagation of the particles of the beamlets; performing a seconddecelerating of the particles of the beamlets after the deflecting ofthe beamlets; and allowing the particles of the beamlets to be incidenton an object surface after the performing of the second decelerating.

The accelerating and decelerating can be achieved by distributing aplurality of electrodes along a path of the beam and the beamlets,respectively, wherein suitably selected voltages are supplied to theelectrodes such that electric fields are generated between adjacentelectrodes. The particles are accelerated and decelerated, respectively,by these electric fields. The electrodes may have a configuration of aplate oriented transverse to the direction of the beam and the beamlets,respectively, wherein the plate is provided with an aperture allowingthe particles to traverse the electrode.

The plurality of particle beamlets can be formed, for example, by aplate oriented transverse to the beam direction such that the beam isincident on the plate. A plurality of apertures are formed in the platesuch that particles of the beam traversing the apertures form theplurality of beamlets downstream of the plate.

The deflecting of the beamlets is performed in order to scan thelocations of incidence of the beamlets on the object surface across thesurface.

According to some embodiments, the deflecting is achieved by operating amagnetic deflector generating time-varying deflection fields bysupplying time-varying electric currents to coils generating themagnetic fields.

According to other exemplary embodiments, the deflection is achieved byelectrostatic deflectors generating time-varying electric deflectionfields, wherein time-varying electric voltages are supplied toelectrodes of the deflector. Since the deflection is performed after theperforming of the first decelerating of the particles, the kineticenergy of the particles is relatively low such that electrostaticdeflectors can be successfully used for achieving a desired amount ofdeflection. Electrostatic deflectors have an advantage over magneticdeflectors in that the generated deflection fields can be readilychanged at very high rates, allowing for rapid scanning of the beamletsacross the object surface.

The second decelerating of the particles is performed in order to adjusta kinetic energy at which the particles are incident on the objectsurface. Typically, this kinetic energy changes from application toapplication and is sufficiently low to avoid damages of the objectduring the irradiation with the particle beamlets, or to improve acontrast of a detected image. For example, the kinetic energy with whichthe electrons are incident on the object surface can be adjusted tooperate at the neutral point of the electron yield at which, on theaverage, each incident electron causes one electron to leave the objectsurface such that a significant charging of the object surface does notoccur. However, the particles travel at significantly higher kineticenergy through the particle beam system before the second deceleratingis performed. The higher kinetic energies reduce the total timenecessary for the particles to traverse the system such that the Coulombinteraction between the particles does not unnecessarily increase adiameter of the particle beam spots formed on the object surface. A highspatial resolution can be achieved, accordingly.

Further embodiments of the present invention provide a charged particlebeam system comprising: a particle beam source configured to generate aparticle beam wherein the particle beam source includes a particleemitter; a first electrode downstream of the particle beam source; amulti-aperture plate downstream of the first electrode; a secondelectrode downstream of the multi-aperture plate; a third electrodedownstream of the multi-aperture plate; a deflector downstream of thethird electrode; an objective lens downstream of the deflector; a fourthelectrode downstream of the deflector; and an object mount configured tomount an object such that a surface of the object is located downstreamof the objective lens; a voltage supply configured to maintain theparticle emitter at a first voltage; the first electrode and/or themulti-aperture plate at a second voltage; the second electrode at athird voltage; the third electrode at a fourth voltage; the fourthelectrode at a fifth voltage; and object mount at a sixth voltage;wherein an absolute value of a first difference between the firstvoltage and the second voltage is greater than a first voltage amount;an absolute value of a second difference between the second voltage andthe third voltage is greater than the first voltage amount; an absolutevalue of a third difference between the third voltage and the fourthvoltage is greater than the first voltage amount; an absolute value of afourth difference between the fourth voltage and the fifth voltage orthe sixth voltage is greater than the first voltage amount; the firstdifference and the second difference have a same sign; the thirddifference and the fourth difference have a same sign; and the firstdifference and the third difference have opposite signs.

Other embodiments of the present invention provide a charged particlebeam system comprising: a particle beam source configured to generate aparticle beam wherein the particle beam source includes a particleemitter; a first electrode downstream of the particle beam source; amulti-aperture plate downstream of the first electrode; a secondelectrode downstream of the multi-aperture plate; a third electrodedownstream of the multi-aperture plate; a deflector downstream of thethird electrode; an objective lens downstream of the deflector; a fourthelectrode downstream of the deflector; and an object mount configured tomount an object such that a surface of the object is located downstreamof the objective lens; a voltage supply configured to maintain theparticle emitter at a first voltage; the first electrode and/or themulti-aperture plate at a second voltage; the second electrode at athird voltage; the third electrode at a fourth voltage; the fourthelectrode at a fifth voltage; and object mount at a sixth voltage;wherein an absolute value of a first difference between the firstvoltage and the second voltage is greater than a first voltage amount;an absolute value of a second difference between the second voltage andthe third voltage is greater than the first voltage amount; an absolutevalue of a third difference between the third voltage and the fourthvoltage is greater than the first voltage amount; an absolute value of afourth difference between the fourth voltage and the fifth voltage orthe sixth voltage is greater than the first voltage amount; the firstdifference and the third difference have a same sign; the seconddifference and the fourth difference have a same sign; and the firstdifference and the second difference have opposite signs.

Further embodiments of the present invention provide a charged particlebeam system comprising: a particle beam source configured to generate aparticle beam wherein the particle beam source includes a particleemitter; a first electrode downstream of the particle beam source; asecond electrode downstream of the first electrode; a third electrodedownstream of the second electrode; a multi-aperture plate downstream ofthe third electrode; a deflector downstream of the third electrode; anobjective lens downstream of the deflector; a fourth electrodedownstream of the deflector; and an object mount configured to mount anobject such that a surface of the object is located downstream of theobjective lens; a voltage supply configured to maintain the particleemitter at a first voltage; the first electrode and/or the secondelectrode at a second voltage; the third electrode at a third voltage;the multi-aperture plate at a fourth voltage; the fourth electrode at afifth voltage; and object mount at a sixth voltage; wherein an absolutevalue of a first difference between the first voltage and the secondvoltage is greater than a first voltage amount; an absolute value of asecond difference between the second voltage and the third voltage isgreater than the first voltage amount; an absolute value of a thirddifference between the third voltage and the fourth voltage is greaterthan the first voltage amount; an absolute value of a fourth differencebetween the fourth voltage and the fifth voltage or the sixth voltage isgreater than the first voltage amount; the first difference and thesecond difference have a same sign; the third difference and the fourthdifference have a same sign; and the first difference and the thirddifference have opposite signs.

Still further embodiments of the present invention provide a chargedparticle beam system comprising: a particle beam source configured togenerate a particle beam wherein the particle beam source includes aparticle emitter; a first electrode downstream of the particle beamsource; a second electrode downstream of the first electrode; amulti-aperture plate downstream of the second electrode; a deflectordownstream of the third electrode; an objective lens downstream of thedeflector; a third electrode downstream of the deflector; and an objectmount configured to mount an object such that a surface of the object islocated downstream of the objective lens; a voltage supply configured tomaintain the particle emitter at a first voltage; the first electrode ata second voltage; the second electrode at a third voltage; themulti-aperture plate at a fourth voltage; the third electrode at a fifthvoltage; and object mount at a sixth voltage; wherein an absolute valueof a first difference between the first voltage and the second voltageis greater than a first voltage amount; an absolute value of a seconddifference between the second voltage and the third voltage is greaterthan the first voltage amount; an absolute value of a third differencebetween the third voltage and the fourth voltage is greater than thefirst voltage amount; an absolute value of a fourth difference betweenthe fourth voltage and the fifth voltage or the sixth voltage is greaterthan the first voltage amount; the first difference and the thirddifference have a same sign; the second difference and the fourthdifference have a same sign; and the first difference and the seconddifference have opposite signs.

The first voltage difference between the particle emitter and the firstelectrode is selected such that the particles are accelerated. When theparticles are electrons, the particle emitter is commonly referred to asa cathode, and the voltage applied to the cathode is lower than thevoltage applied to the first electrode, which is then commonly referredto as an anode.

The second voltage difference between the voltage applied to the firstelectrode and the voltage applied to the second electrode is selectedsuch that the particles are accelerated. The third voltage differencebetween the voltage applied to the second electrode and the voltageapplied to the third electrode is selected such that the particles aredecelerated, and the fourth voltage difference between the voltageapplied to the third electrode and the voltage applied to the fourthelectrode is selected such that the particles are decelerated. A voltagedifference between the particle emitter and the object mount determinesthe landing energy of the particles, i.e. the kinetic energy at whichthe particles are incident on the object surface.

Absolute values of the first, second, third and fourth voltagedifferences can be greater than 10 kV, greater than 20 kV or greaterthan 30 kV.

Similarly, the first and second accelerating of the particles and thefirst and second decelerating of the particles can increase, ordecrease, respectively, the kinetic energy of the particles by more than10 keV, more than 20 keV or more than 30 keV.

According to some embodiments, the method further comprises performing afirst converging of the beam before the deflecting. Since the particlebeam extracted from the particle beam source is generally a divergingbeam, the first converging may reduce a distance between adjacentparticle beam spots on the object surface.

According to exemplary embodiments, the first converging is performedbefore forming of the plurality of beamlets. According to alternativeexemplary embodiments, the first converging is performed after formingof the plurality of beamlets.

According to further exemplary embodiments, the first converging isperformed before the deflecting.

According to further embodiments, the converging is performed such thata crossover of the beamlets is formed. Such crossover is a location orregion along the beam path where the particle beamlets intersect anoptical axis of the system.

According to some embodiments herein, the crossover is formed after thefirst decelerating and before the second decelerating.

According to further embodiments herein, the method further comprisesperforming a second converging of the beamlet after the crossover isformed and before the performing of the second decelerating. The firstand second converging can be performed such that images of the particleemitter of the source are generated on the substrate surface, resultingin small particle beam spots on the substrate surface.

The first and second converging can be achieved by focusing lensesarranged along the particle beam path. According to some embodiments,the focusing lenses are magnetic lenses generating focusing magneticfields.

According to some embodiments, the system comprises a first focusinglens downstream of the beam source and upstream of the deflector.According to some embodiments herein, the first focusing lens ispositioned upstream of the multi-aperture plate.

According to some embodiments, the method comprises performing a thirdaccelerating of the particles of the beamlets before the crossover isformed. Such third accelerating reduces the traveling time of theparticles for traversing the crossover such that an increase of theparticle beam spots on the object surface is avoided or significantlyreduced.

In some embodiments, a third decelerating is performed after forming ofthe crossover, such that the kinetic energy of the particles is alreadyreduced before the second converging is performed.

The third accelerating and the third decelerating may change the kineticenergy of the particles by more than 10 keV, more than 20 keV or morethan 30 keV.

According to some embodiments, the forming of the plurality of beamletsincludes generating of beamlet foci. The beamlet foci are images of aparticle emitter of the source, and the these images can be furtherimaged onto the substrate surface, resulting in small beam spots formedon the substrate surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The forgoing as well as other advantageous features of the disclosurewill be more apparent from the following detailed description ofexemplary embodiments with reference to the accompanying drawings. It isnoted that not all possible embodiments necessarily exhibit each andevery, or any, of the advantages identified herein.

FIG. 1 schematically illustrates basic features and functions of acharged particle beam system;

FIG. 2 schematically illustrates particle beam paths in a chargedparticle beam system according to a first embodiment;

FIG. 3 schematically illustrates particle beam paths in a chargedparticle beam system according to a second embodiment;

FIG. 4 schematically illustrates particle beam paths in a chargedparticle beam system according to a third embodiment;

FIG. 5 schematically illustrates particle beam paths in a chargedparticle beam system according to a fourth embodiment;

FIG. 6 schematically illustrates particle beam paths in a chargedparticle beam system according to a fifth embodiment; and

FIG. 7 schematically illustrates particle beam paths in a chargedparticle beam system according to a sixth embodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In the exemplary embodiments described below, components that are alikein function and structure are designated as far as possible by alikereference numerals. Therefore, to understand the features of theindividual components of a specific embodiment, the descriptions ofother embodiments and of the summary of the disclosure should bereferred to.

FIG. 1 is a schematic diagram symbolically illustrating basic functionsand features of an inspection system using a plurality of particlebeamlets. The inspection system generates a plurality of primaryelectron beamlets which are incident on a substrate to be inspected toproduce secondary electrons emanating from the substrate which aresubsequently detected. The inspection system 1 is of a scanning electronmicroscope type (SEM) using a plurality of primary electron beamlets 3for generating primary electron beam spots 5 on a surface of thesubstrate 7 to be inspected. The inspected substrate 7 can be of anytype and may comprise, for example, a semiconductor wafer, a biologicalsample and an arrangement of miniaturized features of other types. Thesurface of the substrate 7 is arranged in an object plane 101 of anobjective lens 102 of an objective lens system 100.

Insert I₁ of FIG. 1 shows an elevational view of the object plane 101with a regular rectangular array 103 of primary electron beam spots 5formed thereon. In FIG. 1 a number of 25 primary electron beam spots arearranged as a 5×5-array 103. This number of 25 primary electron beamspots is a low number chosen for ease of illustration in the schematicdiagram of FIG. 1. In practice, the number of primary electron beamspots may be chosen substantially higher, such as 20×30, 100×100 andothers.

In the illustrated embodiment, the array 103 of primary electron beamspots 5 is a substantially regular rectangular array with asubstantially constant pitch p₁ between adjacent beam spots. Exemplaryvalues of p₁ can be greater than 1 μm, greater than 10 μm, greater than20 μm or even greater than 50 μm. It is however also possible that thearray 103 is a distorted regular array having different pitches indifferent directions, and the array may also have other symmetries, suchas a hexagonal symmetry.

A diameter of the primary electron beam spots formed in the object plane101 can be small. Exemplary values of such diameter are 1 nm to 5 nm,but they can also be as large as 100 nm or even 200 nm. The focusing ofthe primary electron beamlets 3 to form the primary electron beam spots5 is performed by the objective lens system 100.

The primary electrons incident on the substrate 7 at the beam spots 5produce secondary electrons emanating from the surface of the substrate7. The secondary electrons emanating from the surface of the substrate 7are received by the objective lens 102 to form secondary electronbeamlets 9. The inspection system 1 provides a secondary electron beampath 11 for supplying the plurality of secondary electron beamlets 9 toa charged particle detection system 200. The detection system 200comprises a projection lens arrangement 205 for directing the secondaryelectron beamlets 9 towards a detector 207. The detector is a detectorhaving plural detection elements and may comprise a CCD detector, a CMOSdetector, a scintillator detector, a micro-channel plate, an array ofPIN-diodes, Avalange photodiodes (APD), and others and suitablecombinations thereof.

Insert I₂ of FIG. 1 shows an elevational view of the detector 207,wherein secondary electron beam spots 213 are formed on individualdetection elements 215 which are arranged as an array 217 having aregular pitch p₂. Exemplary values of the pitch p₂ are 10 μm, 100 μm and200 μm.

The primary electron beamlets 3 are generated by a beamlet generationsystem 300 comprising at least one electron source 301, at least onecollimating lens 303, a multi-aperture plate arrangement 305 and a fieldlens 307.

The electron source 301 generates a diverging electron beam 309 which iscollimated by collimating lens 303 to form a beam 311 illuminating themulti-aperture arrangement 305.

Insert I₃ of FIG. 1 shows an elevational view of the multi-aperturearrangement 305. The multi-aperture arrangement 305 comprises amulti-aperture plate 313 having a plurality of apertures 315 formedtherein. Centers 317 of the apertures 315 are arranged in a pattern 319corresponding to the pattern 103 of the primary electron beam spots 5formed in the object plane 101. A pitch p₃ of array 103 may haveexemplary values of 5 μm, 100 μm and 200 μm. Diameters D of theapertures 315 are less than the pitch p₃. Exemplary values of thediameters D are 0.2·p₃, 0.4·p₃ and 0.8·p₃.

Electrons of the illuminating beam 311 traversing the apertures 315 formthe primary electron beamlets 3. Electrons of illuminating beam 311impinging on the plate 313 are intercepted by the plate and do notcontribute to forming the primary electron beamlets 3.

Moreover, the multi-aperture arrangement 305 focuses the individualelectron beamlets 3 such that foci 323 are generated in a plane 325.Insert I₄ of FIG. 1 shows an elevational view of plane 325 with foci 323arranged in a pattern 327. A pitch p₄ of pattern 327 may be equal to ordifferent from the pitch p₃ of pattern 319 of the multi-aperture plate313. A diameter of the foci 323 may have exemplary values of 10 nm, 100nm and 1 μm.

The field lens 307 and the objective lens 102 provide an imaging systemfor imaging the plane 325 onto the object plane 101 to form the array103 of primary electron beam spots 5 on the surface of the substrate 7.

A beam splitter system 400 is provided in the primary electron beam path13 in-between the beam generating system 300 and the objective lenssystem 100. The beam splitter system 400 is also part of the secondaryelectron beam path 11 such that the beam splitter system 400 is locatedin-between the objective lens system 100 and the detection system 200.

Background information relating to such beamlet inspection system andcharged particle components used therein, such as charged particlesources, multi-aperture plates and lenses may be obtained from WO2005/024881, WO 2007/028595, WO 2007/028596 and WO 2007/060017 whereinthe full disclosure of these applications is incorporated herein byreference.

FIG. 2 is a schematic illustration of a charged particle beam system 1 ain which a plurality of charged particle beamlets 3 a are directed ontoa surface of an object 7 a mounted on an object mount 8. In theillustration of FIG. 2, the number of particle beamlets 3 a is three.This low number has been chosen for illustration purposes only, and thenumber of particle beamlets used in practice can be significantlyhigher, as already mentioned above. Moreover, the diameter of thebeamlets is exaggerated relative to the length of the total beam pathbetween a charged particle source 301 a and the surface of the object 7a.

The particle beam source 301 a comprises a particle beam emitter 331which is also referred to as a cathode, since the particles emitted fromthe particle emitter 331 are electrons. The particle beam source 301 acomprises at least one connector 333 connecting the emitter 331 to acontroller 11 of the system 1 a. The controller 11 supplies a heatingcurrent and other necessary signals to the emitter 331 and maintains theemitter 331 at a predefined electric potential by supplying a firstvoltage V1 to the emitter 331.

The beam source 301 a further comprises an extractor electrode 335connected via a connector 337 to the controller 11. The controller 11maintains the extractor electrode 335 at a suitable voltage relative tothe voltage V1 of the emitter 331 such that a diverging particle beam309 a is extracted from the emitter 331.

A first electrode 339 is located downstream of the particle source 301 aalong a beam path of the particle beam 309 a. The first electrode 339 isconfigured as a plate oriented orthogonal to an optical axis 340 alongwhich the particle beam 309 a propagates. The plate has a circularaperture centered on the optical axis 340 and traversed by the beam 309a. The first electrode 339 is connected via a connector 341 with thecontroller 11 which supplies a second voltage V2 to the first electrode.

A voltage difference between the first voltage V1 and the second voltageV2 and a voltage difference between the voltage applied to the extractor335 and the second voltage V2 are selected such that the particles ofthe particle beam 309 a are accelerated after the extraction from theparticle source 301 a. Two arrows between the electrodes 335 and 339 inFIG. 2 represent an accelerating electric field E1 generated between theelectrodes 335 and 339 and which accelerates the particles. A focusingcondenser lens 303 a is located downstream of the first electrode 339.The condenser lens 303 a can be a magnetic lens which is energized bythe controller such that the diverging beam 309 is converged to form aparallel beam 311 a.

A multi-aperture plate 313 a is positioned downstream of the condenserlens 303 a. The multi-aperture plate 313 a has a plurality of apertureswhich are traversed by the particles of the beam 311 a such thatparticle beamlets are generated downstream of the multi-aperture plate313 a. The multi-aperture plate 313 a is connected, via a connector 315,to the controller 11, and the controller 11 maintains the multi-apertureplate 313 at a suitable voltage. In the present example, this voltage isequal to the second voltage V2 applied to the first electrode 339, suchthat no accelerating or decelerating electric fields are generatedbetween the electrode 339 and the multi-aperture plate 313 a, and thekinetic energy at which that particles of the beam 311 a are incident onthe multi-aperture plate 313 a is the kinetic energy to which theparticles have been accelerated after traversing the electric field E1.

A second electrode 343 is positioned downstream of the multi-apertureplate 313 a. The second electrode 343 is configured similar to the firstelectrode 339 and is formed of a plate having a circular aperturecentered at the optical axis 340 and of a size such that all beamletsformed by the multi-aperture plate 313 can traverse the aperture. Thesecond electrode 343 is connected, via a connector 345, to thecontroller 11 and maintained by the controller at a third voltage V3.The third voltage V3 is selected such that an accelerating electricfield E2 is generated between the multi-aperture plate 313 a and thesecond electrode 343. The electric field E2 generated downstream andadjacent to the apertures of the multi-aperture plate accelerates theparticles of the beamlets having traversed the apertures of themulti-aperture plate 313 a and has a function of focusing the particlebeamlets having traversed the multiple apertures such that beamlet foci323 a are formed downstream of the multi-aperture plate 313 a.

A third electrode 347 is positioned downstream of the second electrode343. The third electrode 347 is formed of a plate having an aperturetraversed by the beamlets 3 a and is connected to the controller 11 viaa connector 349. The controller 11 maintains the third electrode 347 ata fourth voltage V4 selected such that a decelerating electric field E3is generated between the second electrode 343 and the third electrode347. The electric field E3 decelerates the particles of the beamletssuch that their kinetic energies are significantly reduced. Further, theelectric field E3 produced between the second and third electrodes 343and 347 has a function of a diverging particle optical lens, such thatadjacent beamlet foci 323 a have a greater distance from each other thanadjacent centers of the apertures of the multi-aperture plate 313 a. Inthe present example, the voltage V4 is 0 V such that the third electrode347 is at ground potential. However, other voltages can be applied tothe third electrode 347 in order to generate a decelerating electricfield E3 upstream of the third electrode 347. The ground potential isthe potential of major components of the system, such as a vacuum vesselenclosing the particle beam path. The ground potential at this portionof the beam path provides advantages regarding the mechanical designsince insulators are not required, and it provides advantages for theelectrostatic scanning system.

A focusing, lens 307 a is positioned downstream of the third electrode347. The focusing lens 303 a can be a magnetic lens. The focusing lens307 a has a function of a field lens and converges the particle beamletssuch that a crossover of the bundle of the particle beamlets 3 a isformed in a region 352 downstream of the field lens 307 a. In thepresent example, the field lens 307 a is positioned upstream of thebeamlet foci 323 a. However, the beamlet foci 323 a can also be formedupstream of the field lens 307 a or within the field lens. The beamletfoci 323 a can be even formed upstream of the third electrode 347.

A deflector arrangement 353 is located downstream of the field lens 307a. The deflector 353 has a function of deflecting the particle beamlets3 a such that the locations of incidence 5 a of the beamlets 3 a on thesurface of the object 7 a can be changed. The deflector arrangement 353comprises a first deflector 354 and a second deflector 355 positioneddownstream of the first deflector 354. The deflector arrangement 353comprises two deflectors 354 and 355 to be able to simultaneously adjustthe position of the location of incidence of the beamlets on the objectsurface and the landing angle of the beamlets on the object surface.Each of the deflectors 354, 355 comprises plural pairs of electrodespositioned on opposite sides of the optical axis 340. The electrodes areconnected, via respective connectors 356, to the controller 11. Thecontroller 11 can apply different voltages to the electrode pairs suchthat deflecting electric fields oriented orthogonal to the optical axis340 are generated between the pairs of electrodes. Time-varying voltagescan be applied to the deflectors 354, 355 in order to scan the array ofparticle beam spots 5 a across the surface of the object 7 a.

A focusing objective lens 102 a is located downstream of the crossover352 and has a function of focusing the particle beamlets 3 a onto thesurface of the object 7 a such that small beam spots 5 a are generatedon the object surface.

A further electrode 359 is positioned upstream of the surface of theobject and has an aperture traversed by the particle beamlets 3 a. Theelectrode 359 can be integrated with components of the objective lens102 a. For example, a pole piece of the objective lens may form theelectrode 359. However, it is also possible to provide the electrode 359as a separate element. The fourth electrode 359 is connected, via aconnector 361 to the controller 11. The controller supplies a fifthvoltage V5 to the fourth electrode 359 such that a decelerating electricfield E4 is generated upstream of the fourth electrode 359. Thedecelerating electric field E4 is generated between the fourth electrode359 and a further electrode 363 positioned upstream of the fourthelectrode 359 and connected, via a connector 365, to the controller 11.The controller 11 supplies a voltage to the further electrode 363selected such that the field generated between the electrodes 363 and359 is decelerating to the particles of the beamlets 3 a. In the presentexample, the voltage applied to the further electrode 363 is the fourthvoltage V4 also applied to the third electrode 347, such that theparticles are maintained at a constant kinetic energy when they traversethe field lens 351, the deflector 353, the crossover 352 and a beamsplitter 400 a illustrated in more detail below.

The further electrode 363 can be integrated with components of theobjective lens 102 a. For example, pole pieces of the objective lens 102a can provide the further electrode 363. However, it is also possiblethat the further electrode 363 is provided by an element separate fromthe objective lens 102 a.

The object mount 8 is connected, via a connector 367, to the controller11, and the controller 11 supplies a sixth voltage V6 to the objectmount 8. The inspected object 7 a is electrically connected to theobject mount 8 and has a sufficient conductivity such that also thesurface of the object 7 a is maintained substantially at the voltage V6.The difference between the sixth voltage V6 and the first voltage V1 atwhich the particle emitter is maintained substantially determines thelanding energy of the particles on the object 7 a, i.e. the kineticenergy at which the particles are incident on the surface of the object7 a. In this context, it is to be noted that the landing energy isfurther influenced by charges locally accumulated on the object surface.In some embodiments, the sixth voltage V6 is selected such that it isequal to the fifth voltage V5 of the fourth electrode 359 positionedupstream of the object surface, such that the particles are not furtheraccelerated or decelerated between the fourth electrode 359 and theobject 7 a.

The particles of the particle beamlets 3 a incident on the object 7 a atthe beam spots 5 a generate secondary particles, such as backscatteredelectrons and secondary electrons, which emanate from the objectsurface. These secondary particles may traverse the fourth electrode 359and are then accelerated in the electric field E4 such that they gain asignificant amount of energy in order to traverse the objective lens 102a. A beam 11 a formed from the secondary particles is then separatedfrom the beamlets 13 a of the primary particles in a beam splitter 400a. The beam splitter 400 a directs the secondary particles towards adetector arrangement 200 a including one detection element 215 a foreach primary particle beam spot 5 a.

Various voltages can be supplied to the emitter 331, the first electrode339, the second electrode 343, the third electrode 347 and the fourthelectrode 359 such that the electric field E1 provided upstream of themulti-aperture plate 313 a is accelerating, the electric field E2provided downstream of the multi-aperture plate 313 a, i.e. the formingof the plurality of beamlets, is accelerating to the particles, and theelectric field E3 provided downstream of the accelerating electric fieldE2 is decelerating and the electric field E4 provided downstream of thedeflector arrangement 353 and after the deflecting of the particles isdecelerating to the particles. According to one example, the voltage V1applied to the emitter 331 is a negative high voltage HV, the voltage V2applied to the first electrode 339 is 0 V, i.e. ground potential, thevoltage V3 applied to the second electrode 343 is a positive highvoltage HV, the voltage V4 applied to the third electrode 347 is 0 V,i.e. ground potential, and the voltage V5 applied to the fourthelectrode 359 is the negative high voltage HV, wherein the voltage V6applied to the object mount 8 can be also the negative high voltage HVor suitably higher in order to adjust the landing energy of theparticles on the object surface to a desired value.

The high voltage HV can be, for example, 10 kV, 20 kV or 30 kV.

FIG. 3 is a schematic illustration of a further charged particle beamsystem 1 b in which a plurality of charged particle beamlets 3 b aredirected onto a surface of an object 7 b mounted on an object mount 8 b.The charged particle beam system 1 b has a configuration similar to theconfiguration of the system illustrated with reference to FIG. 2 above.For example, a divergent particle beam 309 b is extracted from theparticle source 301 b and accelerated by an electric field E1 generatedbetween an extractor electrode 335 b and a first electrode 339 b. Thedivergent beam 309 b is converged by a focusing condenser lens 303 b.While the converged beam downstream of the first focusing or condenserlens was a parallel beam in the embodiment illustrated with reference toFIG. 2 above, the converged beam 311 b of the present example is aconverging beam incident on a multi-aperture plate 313 b provided forforming a plurality of particle beamlets. The particles of the particlebeamlets are accelerated by an electric field E2 provided between themulti-aperture plate 313 b and a second electrode 343 b, such thatbeamlet foci 323 b are generated downstream of the second electrode 343b. A decelerating electric field E3 is provided between the secondelectrode 343 b and a third electrode 347 b subsequent to theaccelerating field E2. After the deceleration in the electric field E3,the particle beamlets traverse a deflector arrangement 353 b, form acrossover 352 b and are converged in a focusing objective lens 102 bsuch that beam spots 5 b are formed on the surface of the object 7 bfrom the particle beamlets 3 b. Further, a decelerating electric fieldE4 is provided upstream of the object surface between a fourth electrode359 b and a further electrode 363 b.

The system 1 b differs from the system illustrated with reference toFIG. 2 above in that a field lens is not provided in a region where thebeamlet foci 323 b are formed. However, the condenser lens 303 b isenergized such that the particle beam 311 b from which the plurality ofbeamlets are formed is a converging beam such that the crossover 352 bis formed downstream of the beamlet foci 323 b.

The system 1 b further differs from the system illustrated withreference to FIG. 2 above in that a fifth electrode 371 is locateddownstream of the deflector arrangement 353 b and upstream of thecrossover 352 b. The fifth electrode 371 has an aperture traversed bythe particle beamlets and is connected, via a connector 373, to acontroller 11 b, which supplies a seventh voltage V7 to the fifthelectrode 371. The seventh voltage V7 is selected such that anaccelerating electric field E5 is generated upstream of the fifthelectrode 371 in order to accelerate the particles of the beamlets suchthat they traverse the region of the crossover 352 b in a shorter timefor avoiding an increase of the beam spots 5 b formed on the objectsurface due to Coulomb interaction. The accelerating electric field E5is generated between the fifth electrode 371 and a further electrode 375provided upstream of the fifth electrode 371. The further electrode 375is connected, via a connector 377, to the controller 11 b. A suitablevoltage can be supplied to the further electrode 375 such that theelectric field E5 generated between the further electrode 375 and thefifth electrode 371 is accelerating to the particles. In the presentexample, the voltage supplied to the further electrode 375 is equal tothe fourth voltage V4 supplied to the third electrode 347 b providedupstream of the deflector arrangement 353 b. As in the previous example,the voltage V4 can be 0 V, i.e. ground potential, such that thedeflector arrangement 353 b can be operated at ground potential,enabling the use of an electrostatic scan deflector not requiring astatic high voltage offset added to the dynamic scan voltage. It is thenadvantageous to embody the deflector arrangement 353 b as anelectrostatic deflector in which deflecting electric fields aregenerated by electrodes 354 b, 355 b located at opposite sides of theoptical axis 340 b.

This advantage does not only apply to the embodiment shown in FIG. 3with a convergent beam at the multi-aperture plate but to the sameextent also applies to embodiments with parallel beam paths or divergentbeam paths at the multi-aperture plate as shown in FIGS. 2 and 4.

The voltage V1 applied to the particle emitter 331 b, the voltage V2applied to the first electrode 339 b, the third voltage V3 applied tothe second electrode 343 b, the fourth voltage V4 applied to the thirdelectrode 347 b, the fifth voltage V5 applied to the fourth electrode359 b and the sixth voltage V6 applied to the object mount 8 b can beselected as illustrated above with reference to FIG. 2.

FIG. 4 is a schematic illustration of a further charged particle beamsystem 1 c in which a plurality of charged particle beamlets 3 c aredirected onto a surface of an object 7 c mounted on an object mount 8 c.The charged particle beam system 1 c has a configuration similar to theconfiguration of the system illustrated with reference to FIG. 3 above.In particular, a divergent particle beam 309 c is extracted from theparticle source 301 c and accelerated by an electric field E1 generatedbetween an extractor electrode 335 c of the particle source 301 c and afirst electrode 339 c. While the divergent beam extracted from thesource is converged by a condenser lens before the plurality of particlebeamlets are formed in the example illustrated with reference to FIG. 3above, it is the divergent beam 309 c extracted from the source 301 cwhich is incident on a multi-aperture plate 313 c in order to form theplurality of particle beamlets in the system 1 c. Since the beam 309 cincident on the multi-aperture plate 313 c is a divergent beam, theparticle beamlets formed downstream of the multi-aperture plate 313 calso diverge from each other. A focusing condenser lens 303 c ispositioned downstream of the multi-aperture plate 313 c such that theparticle beamlets converge relative to each other downstream of thecondenser lens 303 c and form a crossover 352 c before they are focusedby an objective lens 102 c to form beam spots 5 c or a surface of anobject 7 c.

A second electrode 343 c is positioned downstream of the multi-apertureplate 313 c and supplied with a voltage V3 such that an acceleratingelectric field E2 is provided to the particles downstream of themulti-aperture plate 313 c such that beamlet foci 323 c are formeddownstream of the multi-aperture plate 313 c.

A third electrode 347 c is supplied with a voltage V4 selected such thata decelerating electric field E3 is provided to the particles subsequentto the accelerating electric field E2. As in the previous example, thevoltage V4 can be 0 V, i.e. ground potential, such that the condenserlens 303 c and a deflector arrangement 353 c can be operated at groundpotential.

A fourth electrode 359 c supplied with a fifth voltage V5 is providedupstream of the object 7 c for generating a decelerating electric fieldE4.

Similar to the example illustrated with reference to FIG. 3 above, afifth electrode 371 c is provided downstream of the deflector 353 c forgenerating an accelerating electric field E5 such that the particlestraverse the crossover in a shorter time.

While there is only one decelerating electric field E4 provided upstreamof the object in the embodiment illustrated with reference to FIG. 3above, a further decelerating electric field E6 is generated in thesystem 1 c downstream of the crossover 352 c and upstream of a objectivelens 102 c. The sixth electric field is generated between a sixthelectrode 381 located upstream of the objective lens 102 c andconnected, via a connector 383 to a controller 11 c, and a furtherelectrode 385 connected, via a connector 387 to the controller 11 c andsupplied with a suitable voltage. The voltage supplied to the furtherelectrode 385 can be the same voltage as voltage V7 supplied to thefifth electrode 371 c, such that the particles are not accelerated ordecelerated while traversing the crossover 352 c. However, othervoltages can be supplied to the further electrode 385. The voltage V8can be 0 V, i.e. ground potential, such that the objective lens 102 ccan be operated at ground potential.

The other voltages V1, V2, V3, V4, V5, V6 and V7 supplied to the variouselectrodes of system 1 c can be selected similarly as illustrated abovewith reference to FIGS. 2 and 3.

In the embodiment shown in FIG. 2, the crossover 352 of the bundle ofbeamlets is generated in a region upstream of the beam splitter 400 a.However, the crossover can also be generated within or downstream of thebeam splitter 400 a.

FIG. 5 is a schematic illustration of a further charged particle beamsystem 1 d in which a plurality of charged particle beamlets 3 d arefocused on a surface of an object 7 d. The charged particle beam system1 d has a configuration similar to the systems illustrated withreference to FIGS. 2 to 4 above. In particular, a particle emitter 313 dof a particle beam source 301 d is maintained at a first voltage V1, anda diverging particle beam 309 d is extracted from the emitter 331 dusing an extractor electrode 335 d. A first electrode 339 d is locateddownstream of the particle source 301 d and maintained at a voltage V2such that an accelerating electric field E1 is generated between theextractor electrode 335 d and the first electrode 339 d. A condenserlens 303 d, which can be a magnetic lens, is positioned downstream ofthe first electrode 339 d and converges the diverging beam 309 d suchthat a parallel beam 311 d is formed.

A multi-aperture plate 313 d is positioned within the beam 311 d suchthat a plurality of charged particle beamlets 3 d are formed downstreamof the multi-aperture plate 313 d. A second electrode 343 d ispositioned downstream of the multi-aperture plate 313 d. The secondelectrode 343 d has an aperture traversed by the plurality of beamlets 3d and is maintained at an electric potential V3 such that a deceleratingelectric field E2 is generated between the multi-aperture plate 313 dand the second electrode 343 d. In the illustrated example, themulti-aperture plate 313 d is maintained at the same electric potentialV2 as the first aperture plate 339 d. However, other voltages can beapplied to the second electrode 313 d via the terminal 314 d in order togenerate the decelerating electric field E2 between the multi-apertureplate 313 d and the second electrode 343 d. The decelerating electricfield E2 generated at the downstream side of the multi-aperture plate313 d has an effect such that the apertures of the multi-aperture plate313 d have a function of diverging lenses on the beamlets 3 d such thatdiverging particle beamlets 3 d are formed from the incident parallelbeam 311 d downstream of the multi-aperture plate 313 d.

A third aperture plate 347 d traversed by the bundle of the particlebeamlets 3 d is positioned downstream of the second aperture plate 343d. The third aperture plate 347 d is maintained at an electric potentialV4 selected such that an accelerating electric field E3 is generatedbetween the second aperture plate 343 d and the third aperture plate 347d. The accelerating field E3 has a focusing function on the particlebeamlets such that the bundle of the beamlets 3 d forms a crossover 351d and such that the individual diverging beamlets 3 d are converged suchthat beamlet foci 323 d are formed downstream of the third apertureplate 347 d.

A focusing lens 307 d, which can be a magnetic lens, is positioneddownstream of the crossover 351 d in order to reduce a divergence of thebundle of the beamlets 3 d downstream of the crossover 351 d. In thepresent example, the focusing lens 307 d has a focusing power selectedsuch that the beamlets 3 d propagate parallel to each other downstreamof lens 307 d.

The beamlet foci 323 d are imaged onto the surface of the object 7 dpositioned in an object plane 101 d using a further focusing lens 308 dand an objective lens 102 d. The focusing lens 308 d and the objectivelens 102 d can be magnetic lenses.

A further aperture plate 363 d and a fourth aperture plate 359 d arepositioned upstream of the object plane 101 d. The fourth aperture plate359 d is maintained at a voltage V5 and the further aperture plate 363 dis maintained at a suitable voltage selected such that a deceleratingelectric field E4 is generated between the further aperture plate 363 dand the fourth aperture plate 359 d. In the present example, the voltageapplied to the further electrode 363 d is equal to the voltage V4applied to the third aperture plate 347 d. However, the furtherelectrode 363 d can be maintained at under suitable voltages such thatthe decelerating electric field E4 is generated between the apertureplate 363 d and 359 d.

A further crossover 352 d of the bundle of the particle beamlets 3 d isformed between the lenses 308 and 102 d. A deflector arrangement 353 dis positioned between the lens 308 and the crossover 352 d. However, thedeflector arrangement 353 d can also be located at other positionsbetween the second aperture plate 347 d and the object surface 101 d.Moreover, the focusing power of the lenses 307 d and 308 can be combinedinto one focusing lens.

The voltage V1 can be a negative high voltage, the voltage V3 can be anegative high voltage, the voltage V6 can be negative high voltage, andthe voltages V2, V4 and V5 can be voltages close to ground voltage, suchthat the beam deflector arrangement 353 d can be operated close to or atground voltage. In the illustrated embodiment, the following voltagesare selected: V1=30 kV, V2=0 kV, V3=20 kV, V4=0 kV and V6=−29 kV,wherein the voltage V5 is selected such that it is equal to V6 or suchthat at least a small decelerating field is generated between theaperture plate 359 d and the object 7 d. It is also possible to omit thefurther aperture plate 363 d and to select the voltage V5 such that thedecelerating electric field E4 is generated between the fourth apertureplate 359 d and the object 7 d.

FIG. 6 is a schematic illustration of a further charged particle beamsystem 1 e in which a plurality of charged particle beamlets 3 e aredirected onto a surface of an object 7 e. The charged particle beamsystem 1 e has a configuration similar to the systems illustrated withreference to FIGS. 2 to 5 above. For example, a divergent particle beam309 e is extracted from a particle source 301 e and accelerated by anelectric field E1 generated between an extractor electrode 335 e and afirst electrode 339 e. A second electrode provided by a secondsingle-aperture plate 343 e is positioned in the beam path of thedivergent beam 309 e. A third electrode or aperture plate 347 e ispositioned downstream of the second aperture plate 343 e. The thirdaperture plate 347 e is maintained at an electric potential V3 selectedsuch that an accelerating field E2 is generated between the electrodes343 e and 347 e. The electric voltage supplied to the second apertureplate 343 e via a terminal 345 e can be equal to the voltage V2, or itcan be different from the voltage V2. The accelerating field E2 has afocusing function on the diverging beam 309 e such that a convergingbeam 311 e is formed. Additional focusing lenses, such as magneticfocusing lenses, can be positioned between the first and second apertureplates 339 e, 343 e in order to provide additional focusing power on thediverging beam 309 e.

A multi-aperture plate 313 e is positioned downstream of the thirdaperture plate 347 e and maintained at an electric potential V4 suchthat a decelerating electric field E3 is generated between the thirdaperture plate 347 e and the multi-aperture plate 313 e. Thedecelerating electric field E3 has a function of a diverging lens on theconverging beam 311 e such that a parallel beam 312 e is formed which isincident on the multi-aperture plate 313 e. The apertures provided inthe multi-aperture plate 313 e allow the particle beamlets 3 e to passthrough the multi-aperture plate 313 e. The decelerating electric fieldE3 generated on the upstream side of the multi-aperture plate 313 e hasa result that the apertures of the multi-aperture plate 313 e perform afocusing function on the particle beamlets 3 e generated from theincident parallel beam 312 e, such that beamlet foci 323 e are formeddownstream of the multi-aperture plate 313 e. The beamlet foci 323 e areimaged onto the surface of the object 7 e positioned at the object plane101 e. The components shown in FIG. 6 for this purpose have a similarconfiguration to the corresponding components of the embodimentsillustrated with reference to FIGS. 2 to 5 above and will not be furtherillustrated in detail here. Reference should be made to the precedingspecification, accordingly. It is to be noted that a decelerating fieldE4 is generated upstream of the object 7 e between two electrodes 363 eand 359 e or between an electrode and the object 7 e itself.

The voltage V1 can be a negative high voltage, the voltage V2 can beclose to or equal to ground potential, the voltage V3 can be a positivehigh voltage, the voltage V4 can be close to or equal to groundpotential, and the voltage V6 can be a negative high voltage. In thepresent example, the following voltages are selected: V1=−30 kV, V2=0kV, V3=+20 kV, V4=0 kV and V6=−29 kV.

FIG. 7 is a schematic illustration of a further charged particle beamsystem 1 f in which a plurality of charged particle beamlets 3 f aredirected onto a surface of an object 7 f mounted on an object mount 8 f.The charged particle beam, system 1 f has a configuration similar to thesystems illustrated with reference to FIGS. 2 to 6 above. For example, adivergent particle beam 309 f is extracted from a particle source 301 fand accelerated by an electric field E1 generated between an extractorelectrode 335 f and a first electrode provided by a single-apertureplate 339 f. For this purpose, a particle emitter 331 f of the particlesource 301 f is maintained at an electric potential V1, and the firstaperture plate 339 f is maintained at a potential V2. A second apertureplate 343 f is positioned downstream of the first aperture plate 339 fand maintained at a voltage V3 selected such that a deceleratingelectric field E2 is generated between the first and second electrodes339 f and 343 f. A multi-aperture plate 313 f is positioned downstreamof the second aperture plate 343 f and maintained at an electricpotential V4 selected such that an accelerating electric field E3 isgenerated between the single-aperture plate 343 f and the multi-apertureplate 313 f. The decelerating electric field E2 generated on theupstream side of the second aperture plate 343 f and the acceleratingelectric field. E3 provided on the downstream side of the secondaperture plate 343 f result in that a focusing lens function is providedon the diverging beam 309 f. This focusing function 309 f converges thediverging beam 309 f such that a parallel beam 311 f is formed. Theparallel beam 311 f is incident on the multi-aperture plate 313 f. Theaccelerating electric field E3 provided on the upstream side of themulti-aperture plate 313 f results in that a diverging lens function isprovided to each of the particle beamlets 3 f traversing the aperturesof the multi-aperture plate 313 f. Therefore, the particle beamlets 3 fgenerated from the incident beam 311 f are diverging particle beamlets 3f. At positions downstream of the multi-aperture plate 313 f, theparticle beamlets 3 f appear to originate from virtual beamlet foci 323f positioned upstream of the multi-aperture plate 313 f as indicated bydotted lines in FIG. 7. The virtual beamlet foci 323 f are imaged ontothe surface of the object 7 f positioned in an object plane 101 f usingimaging optics configured similar to the imaging optics illustrated withreference to FIGS. 2 to 6 above. It is to be noted that a deceleratingelectric field E4 is provided upstream of the object 7 f, wherein thedecelerating electric field E4 can be generated between electrodes 363 fand 359 f as shown in FIG. 7, or between an electrode and the object 7 fitself. Moreover, a deflector arrangement 353 f can be positioned at asuitable location along the beam path between the virtual beamlet foci323 f and the object surface 101 f.

The voltage V1 can be a negative high voltage, the voltage V2 can beclose to or equal to ground potential, the voltage V3 can be a negativehigh voltage, the voltage V4 can be close to or equal to groundpotential, and the voltage V6 can be a negative high voltage. In thepresent example, the following voltages are selected: V1=−30 kV, V2=0kV, V3=−20 kV, V4=0 kV and V6=−29 kV.

In the particular embodiments illustrated above, it is to be noted thatsome of the electrodes are maintained at ground potential while theFigures indicate separate terminals connected to the controller tomaintain the respective electrodes at desired voltages. It is apparentthat, if the desired voltages are 0 kV, separate terminals connected tothe controller can be omitted and that the electrodes maintained atground potential may have a suitable connection to ground.

While the disclosure has been described with respect to certainexemplary embodiments thereof, it is evident that many alternatives,modifications and variations will be apparent to those skilled in theart. Accordingly, the exemplary embodiments of the disclosure set forthherein are intended to be illustrative and not limiting in any way.Various changes may be made without departing from the spirit and scopeof the present disclosure as defined in the following claims.

The invention claimed is:
 1. A charged particle beam system, comprising: a particle beam source configured to generate a particle beam wherein the particle beam source includes a particle emitter; a first electrode downstream of the particle beam source; a multi-aperture plate downstream of the first electrode; a second electrode downstream of the multi-aperture plate; a third electrode downstream of the second electrode; a deflector downstream of the third electrode; an objective lens downstream of the deflector; a fourth electrode downstream of the deflector; and an object mount configured to mount an object such that a surface of the object is located downstream of the objective lens; a voltage supply configured to maintain the particle emitter at a first voltage; the first electrode and/or the multi-aperture plate at a second voltage; the second electrode at a third voltage; the third electrode at a fourth voltage; the fourth electrode at a fifth voltage; and object mount at a sixth voltage; wherein an absolute value of a first difference between the first voltage and the second voltage is greater than a first voltage amount; an absolute value of a second difference between the second voltage and the third voltage is greater than the first voltage amount; an absolute value of a third difference between the third voltage and the fourth voltage is greater than the first voltage amount; an absolute value of a fourth difference between the fourth voltage and the fifth voltage or the sixth voltage is greater than the first voltage amount; the first difference and the second difference have a same sign; the third difference and the fourth difference have a same sign; and the first difference and the third difference have opposite signs.
 2. The particle beam system of claim 1, wherein the first voltage amount is greater than at least one of 10 kV, 20 kV and 30 kV.
 3. The particle beam system of claim 1, wherein the deflector comprises plural electrodes configured to generate an electric deflection fields oriented transverse to a direction of propagation of the particles of the beamlets.
 4. The particle beam system of claim 1, further comprising a first magnetic focusing lens downstream of the beam source and upstream of the deflector.
 5. The particle beam system of claim 4, wherein the first focusing lens is positioned upstream of the multi-aperture plate.
 6. The particle beam system of claim 4, wherein a crossover of a bundle of particle beamlets is formed downstream of the multi-aperture plate upstream of the fourth electrode.
 7. The particle beam system of claim 4, further comprising a second focusing lens downstream of the crossover.
 8. The particle beam system of claim 7, further comprising a third focusing lens downstream the multi-aperture plate and upstream of the crossover.
 9. The particle beam system of claim 6, further comprising a fifth electrode downstream of the deflector and upstream of the crossover, wherein the voltage supply is further configured to maintain the fifth electrode at a seventh voltage; wherein an absolute value of a fifth difference between the fourth voltage and the seventh voltage is greater than a second voltage amount; and wherein the first difference and the fifth difference have a same sign.
 10. The particle beam system of claim 1, further comprising a detector configured to detect electrons originating from the surface of the object, and wherein the particle beam system is a multi-beam microscope.
 11. A charged particle beam system, comprising: a particle beam source configured to generate a particle beam wherein the particle beam source includes a particle emitter; a first electrode downstream of the particle beam source; a multi-aperture plate downstream of the first electrode; a second electrode downstream of the multi-aperture plate; a third electrode downstream of the second electrode; a deflector downstream of the third electrode; an objective lens downstream of the deflector; a fourth electrode downstream of the deflector; and an object mount configured to mount an object such that a surface of the object is located downstream of the objective lens; a voltage supply configured to maintain the particle emitter at a first voltage; the first electrode and/or the multi-aperture plate at a second voltage; the second electrode at a third voltage; the third electrode at a fourth voltage; the fourth electrode at a fifth voltage; and object mount at a sixth voltage; wherein an absolute value of a first difference between the first voltage and the second voltage is greater than a first voltage amount; an absolute value of a second difference between the second voltage and the third voltage is greater than the first voltage amount; an absolute value of a third difference between the third voltage and the fourth voltage is greater than the first voltage amount; an absolute value of a fourth difference between the fourth voltage and the fifth voltage or the sixth voltage is greater than the first voltage amount; the first difference and the third difference have a same sign; the second difference and the fourth difference have a same sign; and the first difference and the second difference have opposite signs.
 12. The particle beam system of claim 11, wherein the first voltage amount is greater than at least one of 10 kV, 20 kV and 30 kV.
 13. The particle beam system of claim 11, wherein the deflector comprises plural electrodes configured to generate an electric deflection fields oriented transverse to a direction of propagation of the particles of the beamlets.
 14. The particle beam system of claim 11, further comprising a first magnetic focusing lens downstream of the beam source and upstream of the deflector.
 15. The particle beam system of claim 14, wherein the first focusing lens is positioned upstream of the multi-aperture plate.
 16. The particle beam system of claim 14, wherein a crossover of a bundle of particle beamlets is formed downstream of the multi-aperture plate upstream of the fourth electrode.
 17. The particle beam system of claim 16, further comprising a second focusing lens downstream of the crossover.
 18. The particle beam system of claim 17, further comprising a third focusing lens downstream the multi-aperture plate and upstream of the crossover.
 19. The particle beam system of claim 11, further comprising a detector configured to detect electrons originating from the surface of the object, and wherein the particle beam system is a multi-beam microscope.
 20. A charged particle beam system, comprising: a particle beam source configured to generate a particle beam wherein the particle beam source includes a particle emitter; a first electrode downstream of the particle beam source; a second electrode downstream of the first electrode; a third electrode downstream of the second electrode; a multi-aperture plate downstream of the third electrode; a deflector downstream of the third electrode; an objective lens downstream of the deflector; a fourth electrode downstream of the deflector; and an object mount configured to mount an object such that a surface of the object is located downstream of the objective lens; a voltage supply configured to maintain the particle emitter at a first voltage; the first electrode and/or the second electrode at a second voltage; the third electrode at a third voltage; the multi-aperture plate at a fourth voltage; the fourth electrode at a fifth voltage; and object mount at a sixth voltage; wherein an absolute value of a first difference between the first voltage and the second voltage is greater than a first voltage amount; an absolute value of a second difference between the second voltage and the third voltage is greater than the first voltage amount; an absolute value of a third difference between the third voltage and the fourth voltage is greater than the first voltage amount; an absolute value of a fourth difference between the fourth voltage and the fifth voltage or the sixth voltage is greater than the first voltage amount; the first difference and the second difference have a same sign; the third difference and the fourth difference have a same sign; and the first difference and the third difference have opposite signs.
 21. The particle beam system of claim 20, wherein the first voltage amount is greater than at least one of 10 kV, 20 kV and 30 kV.
 22. The particle beam system of claim 20, wherein the deflector comprises plural electrodes configured to generate an electric deflection fields oriented transverse to a direction of propagation of the particles of the beamlets.
 23. The particle beam system of claim 20, further comprising a first magnetic focusing lens downstream of the beam source and upstream of the deflector.
 24. The particle beam system of claim 23, wherein a crossover of a bundle of particle beamlets is formed downstream of the multi-aperture plate upstream of the fourth electrode.
 25. The particle beam system of claim 24, further comprising a second focusing lens downstream of the crossover.
 26. The particle beam system of claim 20, further comprising a detector configured to detect electrons originating from the surface of the object, and wherein the particle beam system is a multi-beam microscope.
 27. A charged particle beam system, comprising: a particle beam source configured to generate a particle beam wherein the particle beam source includes a particle emitter; a first electrode downstream of the particle beam source; a second electrode downstream of the first electrode; a multi-aperture plate downstream of the second electrode; a deflector downstream of the multi-aperture plate; an objective lens downstream of the deflector; a third electrode downstream of the deflector; and an object mount configured to mount an object such that a surface of the object is located downstream of the objective lens; a voltage supply configured to maintain the particle emitter at a first voltage; the first electrode at a second voltage; the second electrode at a third voltage; the multi-aperture plate at a fourth voltage; the third electrode at a fifth voltage; and object mount at a sixth voltage; wherein an absolute value of a first difference between the first voltage and the second voltage is greater than a first voltage amount; an absolute value of a second difference between the second voltage and the third voltage is greater than the first voltage amount; an absolute value of a third difference between the third voltage and the fourth voltage is greater than the first voltage amount; an absolute value of a fourth difference between the fourth voltage and the fifth voltage or the sixth voltage is greater than the first voltage amount; the first difference and the third difference have a same sign; the second difference and the fourth difference have a same sign; and the first difference and the second difference have opposite signs.
 28. The particle beam system of claim 27, wherein the first voltage amount is greater than at least one of 10 kV, 20 kV and 30 kV.
 29. The particle beam system of claim 27, wherein the deflector comprises plural electrodes configured to generate an electric deflection fields oriented transverse to a direction of propagation of the particles of the beamlets.
 30. The particle beam system of claim 27, further comprising a first magnetic focusing lens downstream of the beam source and upstream of the deflector.
 31. The particle beam system of claim 30, wherein the first focusing lens is positioned upstream of the multi-aperture plate.
 32. The particle beam system of claim 30, wherein a crossover of a bundle of particle beamlets is formed downstream of the multi-aperture plate upstream of the fourth electrode.
 33. The particle beam system of claim 31, further comprising a second focusing lens downstream of the crossover.
 34. The particle beam system of claim 27, further comprising a detector configured to detect electrons originating from the surface of the object, and wherein the particle beam system is a multi-beam microscope. 